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Exploring as ecotypes of more than 280 grasses
Exploring new wild plant species of
economic importance and tolerant of harsh environmental conditions in arid
countries may be a viable option to improve forage yield.. The present study was
conducted during two consecutive years and aimed to investigate the nutritional
values of eleven selected wild fodder species, six annuals and five perennials.
Detailed analysis for the nutritional values during two different seasons, for
perennials and two different growth stages for annuals were presented. The
results showed that most studied plants own high nutritional values compared to
earlier studies on taxonomically related
species growing in different arid areas. The mean content of dry matter, ash,
crude protein and lipids were 27%. 13%, 14% and 3.5%, respectively. Neutral
detergent fiber, acid detergent fiber, lignin, cellulose and hemicellulose were
44%, 26.5 %6.2%, 20.2 and 13.7%, respectively. The studied species recorded 43
and 49 as mean percent’s in vitro dry matter disappearance for perennials and
annuals, respectively. In general, there were slightly differences between the
two years for both perennials and annual species and significant differences
between different seasons for perennials and between growth stages for annuals.
The study strongly recommends further detailed experimental studies on A.
graecizan, Boerhavia diffusa and Cymbopogon schoenanthus,
which showed more crude protein, low fiber
content and high IVDMD, as unconventional forage crops in arid lands.
Key words: Forage; Aridity; flora;
Saudi.
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Introduction
Saudi Arabia Kingdom
completely is located in arid and semi-arid dry region (24.1631° N, 43.6021° E.),
with an annual rainfall ranging from zero to 100 mm/year and consider one of
the poorest nations in terms of natural renewable water resources (De Nicola et
al., 2015). Flora of Saudi Arabia contains most aridity tolerant plants in the
world and possesses a unique genetic diversity as ecotypes of more than 280
grasses and legumes (Rao, 2013). The richness of the native flora in the
western and southwestern region of Saudi Arabia in plant relatives of
cultivated crops and fodders presents a genetic diversity that must not be
ignored (Alsherif et al., 2013; Alsherif & Fadl, 2016; Rao, 2013). Grazing
of wild plants from the desert supplements the fundamental and the most conventional
source for livestock production in Saudi Arabia. Although the presence of many
animal resources estimated to be more than 16 million heads (Bakhashwain & Abusuwar,
2011), feeding and browsing resources for livestock are very low. The policy of
fodder production in the Kingdom estimated that rangeland produces about twenty
million tons, dry matter, of which only ten million tons are edible and handy for
livestock feed, enough for just 50% of the animal units in Saudi Arabia,
indicating the presence of a feed gap (Bakhashwain & Abusuwar, 2011).
Varieties of new resources need to
be tapped to fill the basic needs for food and fodder request of increasing
population pressure in light of limited available resources and food deficiency
(Di Virgilio et al., 2015; Naah & Guuroh, 2017). Wild nutritive species
cultivation expected to be important sources for the forage improvement
programs in arid lands because of their adaptation to harsh environmental
conditions, so they are expect to be important sources for the crop improvement
programs (Alsherif, 2009; Walker et al., 2014). Although the natural vegetation
of Saudi`s desert comprises considerable numbers of palatable species rich in
their nutritive values that may consider reliable natural resources for fodder
production (Alsherif et al., 2013), few
studies have dealt with this subject (Bakhashwain et al., 2010), and it received
little attention. Therefore, the present study aimed to (1) explore some wild
fodders, which grow naturally in the prevailing environmental conditions increased
ruminant production in arid environment, (2) study the effects of season for
perennials and growth stage for annuals on their nutritional values.
Material and Methods
Study area
The study was carried out in Khulais
area, Western Saudi Arabia, which is located between 39° 15` and 40° E and
latitudes 22° and 22° 30` N; its elevation ranged between 5 and 35 m above sea
level (Fig. 1). The area characterized by hot arid desert type climate with
scarce rainfalls and an average annual temperature of 27.7°C. The relative
humidity ranges between a maximum of 57% during August and April, and a minimum
of 37% during May and June (Table 1). The area is only used for grazing animals,
it was divided into five sites to include the entire representative,
topographic and physiographic condition; all selected species grow naturally in
all these sites (Table 2). The vegetation of the studied area is a
characteristic type of the natural plant life of the arid land. It is formed
mainly of xerophytic shrubs and undershrubs, e.g. Leptadenia, Indigofera,
Lycium, tough grasses, like Panicum, and a few trees of different
height, e.g. Acacia. In rainy times, short-lived plants (annuals)
probably alter the desert from yellow color into a green (Appendix).
Soil samples and analyses
Five soil samples were collected from zero to 50 cm depth for every
site. Soil texture was detected via Bouyoucos hydrometer procedure. Soil water extracts
of 1:2.5 were prepared for determinations of soil pH using pH meter Model HI
8519, and electrical conductivity (soil salinity) using CMD 830 WPA
conductivity meter. Soluble chlorides, Sulphates, and bicarbonates were
determined according to Jackson (1962). Sodium and potassium cations were
estimated using flame photometer (Allen et al., 1986). While Calcium and
magnesium cations were determined using EDTA (0.01N) according to Jackson
(1962).
Samples selection and collection
A wide survey was completed
throughout the period of January 2015 to December 2016. Eleven wild fodder
species, five perennials and six annuals, were selected according to its
palatability and Bedouin knowledge; it has a good reputation among animal
breeders and prefer them to other plants. The selected perennial species were
Ochradenus baccatus Del., Cadaba farinosa Frossk., Panicum
turgidum Forssk., Cymbopogon schoenanthus (L.) Spreng. and Pennisetum
divisum (J.F. Gmel.) Henrard, while the annual species were Boerhavia
diffusa L., Astragalus vogelii (Webb) Bornm., Convolvulus deserti
Hochst. & Steud., Amaranthus graecizan L., Gynandropsis gynandra
(L.) Briq.,Ann. And Indigofera hoschstettei Baker.
Ten fodder samples representing
different parts of the aerial shoot system (young shoot for perennials) were
harvested from each site for each season (for perennials) and for each growth
stage (for annuals) within their distribution in the field. In each year samples
collection was done from the different sites during two different seasons
(autumn and spring) for the perennials and at different two growth stages
(vegetative and fruiting stages) for annuals, then pooled together to form a
single composite sample, then air-dried and stored in glass bottles.
Chemical analysis
For chemical estimation, samples
were grind to push through one mm screen in a CyclotecTM 1093 Sample Mill (Foss
Companies, Hillerød, Denmark). Samples were analyzed for dry matter (oven-dried
at 60 ?C for 48 h), ash (# 924.05) and ether extracts (EE) (# 954.02) according
to Association of Official Analytical Chemists (AOAC) (1990). The crude protein
(CP) in the fodder samples was separated as proposed by Cornell Net
Carbohydrate and Protein System; CNCPS (Licitra et al., 1996). In vitro dry
matter disappearance (IVDMD) was determined by a modified two-stage Tilley and
Terry procedure (Galyean, 1997). Ash-free neutral detergent fiber (NDFom) was
determined without use of sodium sulphide or amylase according to Van Soest et
al. (1991). Acid detergent fiber (ADFom) was determined (# 973.18; AOAC, 1990)
and expressed exclusive of residual ash. Lignin (sa) was determined by
solubilization of cellulose with 720 g/kg sulphuric acid (Robertson and Van
Soest, 1981). Cellulose and hemicellulose were determined sequentially
according to procedures of Van Soest et al. (1991). Calcium was detected by
atomic absorption, Na and K by the flame emission spectrometer. Phosphorus and
magnesium were determined by spectrophotometer.
Statistical analysis
A minimum of ten observations was
pooled of five replicates for each species to calculate the average values and
standard errors. SPSS software was used to estimate the least significant
differences of variation among the means of plant parameters using one-way
analysis of variance.
Results
Nutritional value of the studied
species
The majority of the studied species
recorded high nutritive values and exhibited significant differences (P<
0.05) for all nutritional values among species. The majority of the studied
species recorded more than 35% of the dry matter content while a few species
recorded less than 30 % (Fig. 2). Annual species recorded 15% as mean ash
content (Fig. 2), while the mean ash content of perennials exhibited 8.4%. The mean
value of ash content was about 12%; ranged between 5.08 and 22.4%. The lowest ash
value was recorded by O. baccatus and G. gynandra showed the
highest value. Most species were rich in their protein contents and ranged
between 4.6% and 18.5%, with G. gynandra showed the highest value
followed by B. diffusa and A. graecizan (Fig. 2).
Ether
extracts (EE) were found with an average 4.3% (Fig. 3); the highest content was
detected by P. turgidum (Fig. 3). The high values of NDFom were
exhibited by the three perennial grass species; P. turgidum, P.
divisum and C. schoenanthus (Fig. 3). G. gynandra, A.
vogelli and A. graecizan revealed the lowest NDFom mean
values, 39.6, 47.6 and 49.8%, respectively. Perennial species showed the highest values
for ADFom while annual species, G. gynandra, A. graecizan
and B. diffusa had the lowest values (Fig. 3). Lignin(sa)
contents were found within the range 3.7 and 17.3% (Fig. 4). The lowest value
of lignin was recorded by A. graecizan, while P. turgidum had the
highest one. Lignin(sa) content was varied widely also within the two
leguminous species (Fig. 4). G. gynandra displayed the lowest values for
cellulose and hemicellulose, 12.8% and 11.7%, respectively (Fig. 4) at both
growth stages, while P. turgidum showed the highest values, 37.6% and
24% in the two seasons, respectively. The amounts of the macro-elements (Ca, P,
Mg, Na and K) varied considerably between the studied species (Tables 3 and 4),
Phosphorus contents exhibited a range 0.22- 0.87%, and the highest amount was
recorded by P. turgidum, while B. diffusa showed the minimum
value. Calcium content exhibit mean value around 1%, while all species had K
level more than 1.5% (Tables 3 and 4). Sodium level recorded mean value about
0.05% for all species; the highest amounts (0.09%) were detected by C.
schoenanthus and P. divisum. The Mg detected in the present study ranged between 0.31% (O.
baccatus) and 0.87% (C. deserti).
A. graecizan showed a high value of IVDMD (about 65%), followed by B. diffusa
and C. schoenanthus 61.1% and 60.1%, respectively (Fig. 5), while
G. gynandra exhibited the lowest value (35.1%) followed by C.
deserti (41.3%) and C. farinosa (45.1%).
Effect of seasons for perennials and
growth stage for annuals on nutritional values
In general, results showed significantly
differences between different seasons for perennials and between different
growth stages for annuals. On contrast, slightly differences were detected between
the two years for both perennials and annual species.
Dry matter, ash, lipid,
carbohydrates, IVDMD and crude protein of perennial species exhibited
significant increases, while all fiber types showed significant decreases in
spring season.
Carbohydrates, IVDMD and crude protein of
annual species recorded significant increases, while all fiber types, Dry
matter, ash and lipid contents exhibited significant decreases at vegetative
stages.
Discussion
Dry matter contents reported in the present study were higher than
those recorded earlier in a neighboring country, the United Arab Emirates,
(Shaltout et al., 2008), indicating that they could be sources of reliable and
affordable to feed the ruminants in Saudi arid lands. The recorded high DM
content could be attributed to their dry environment with limited soil water
content. It is well known that plants in dry areas with high dry weight/ fresh
weight ratio. High ash content reported by G. gynandra in this study may
be due to its high uptake ability to mineral elements (Sillanpaa, 1982). Tropical
forages characterized by low protein level during the long dry season, so
protein consider one of the limiting factor in animal intake and performance
(Minson, 1982) and proposed to be an indicator of the nutritional value of
plants as food for ruminants. All studied species, except C. schoenanthus,
showed protein content higher than the lower limit for livestock requirements,
which were reported by Barker and Collins (2003). The high-recorded ether
extracts content of P. turgidum could be due to samples collected at
seed formation stage, which has oil. Results
of K and Ca contents supported the finding of Khan et al. (2007), who reported
that K concentration varied in tropical grasses based on sampling period and Ca
contents of arid pastures were slightly higher than the least recommended
levels in the ruminant diets. Mg and P contents in the studied species
supported the findings of Skerman and Riveros (1990), who reported that Mg
content of tropical plants varied from 0.04 to 0.90% with a mean of 0.36% and P
content in tropical grasses varied from 0.02 to 0.06% of plant dry matter due
to available P in the soil. The high
mineral content in the present species could be due to its relatively higher
uptake from coarse-textured soils with a low cation exchange capacity. It is
well known that factors like soil, climate, maturity phase; season and
management participate to change in the mineral concentrations in fodders (Khan
et al., 2005; McDowell et al., 1983). The high NDFom, ADFom and lignin(sa)
contents reported by grasses and O. baccatus are probably due to the
decline of leaf: stem ratio. Revell et al. (1994) reported a positive correlation
between CP and digestibility, in addition it had been reported that cell wall
component, NDF, ADF and lignin were negatively correlated with IVDMD in tree
leaves (Kambashi et al. 2014).
The majority of
the studied species showed nutritional values higher than those reported
earlier by other wild, taxonomically related, species. Azim et al. (2011)
recorded lower protein content of I. gerardii, grown in Pakistan, than
the studied species (I. hochstetteri) by 14%. Kuria et al. (2005) found
that protein content of I. spinosa and I. cliffodiana, grown in
Kenya, lower than the studied species (I. hochstetteri) by 42% and 18%,
respectively; they found also NDF, ADF and ADL of I. spinosa were higher
than those recorded in the current species by 41%, 51% and 60%, respectively.
In the present study B. diffusa recorded higher crude protein than the
same species grown in Nigeria (Ujowundu et al., 2008). A. graecizan
exhibited higher IVDMD and lipid content in comparison with A. hybridus,
collected from Congo, by 22% and 47%, respectively (Kambashia et al., 2014).
Two Pennisetum species, one from Benin, P. purpureum and the
other from Pakistan, P. orientale, recorded higher protein contents than
that obtained by the current study species, P. divisum, by 38% and 6%,
respectively, while the current species (P.turgidum) characterized by
higher IVDMD than both previous species by 126% (Kambashia et al., 2014; Sarwar
et al. 2006). A. vogelii in the present study recoded Protein content
lower than A. ponticus, collected from Iran, by 38%, as much as A.
sulcatus, collected from Canada, (Schutte & Lauriault, 2015) and higher
than A. ponticus, collected from Moldova , by 56% ( Teleuta & Titei,
2014). With regard to C. deserti, Schutte and Lauriault (2015) estimated
higher protein and lower fiber content for C. arvensis collected from
Iran. C. farinosa in the present study recorded lower protein and fiber
content in comparison with the same species collected from Kenya (Kuria et al.,
2005).
Effect of season and growth stage on
nutritive values
The current study showed higher Dry
matter, ash, lipid, carbohydrates, IVDMD and crude protein, contents of the
forage material in the spring, versus autumn, for all perennial species. Pearson
and Ison, (1997) reported that high temperature increased cell wall
constituents and lignification, while decreasing CP and soluble carbohydrate
concentration, as well as digestibility.
Carbohydrates, IVDMD and crude
protein of annual species increased while all fiber types, Dry matter, ash and
lipid contents exhibited decreases at vegetative stages due to the changes
associated with the advancing stage of maturity of individual species (Ammar et
al., 1999; Moore & Jung, 2001). Current results are also consistent with previously
published data (e.g. Mahala et al., 2009; Michiels et al., 2000) that suggest
that CP often declines with increasing plant structural constituents (NDF, ADF
and lignin) and increasing age of maturity.
Growth stage significantly affected
nutritive values of annual species. One of the important factors influencing
the feeding value of forage is its stage of maturity at time of harvesting (Fulkerson
et al. 1999; Rawnsley et al., 2002). As a result of investigations carried out
over a number of years, it is an accepted fact that forage decreases in overall
nutritive value with increasing maturity (Bosch et al., 1992; Lloyd et al.,
1961; Osbourn, 1980). It is also well known that this decrease is due, in great
part, to a decrease in the nutrient content of the forage together with a
concomitant increase in the fibrous components and general lignification. Plant
maturity was found to impact neutral detergent fiber (NDF), acid detergent
fiber (ADF), lignin(sa), CP and nitrate content of amaranth forage (Sleugh et
al., 2001).
Conclusion
It is worth stating that the
majority of the studied species showed nutritional values higher than reported
earlier by other related species in different arid lands. Therefore, the high
protein level of the studied species nominate these plants, especially A.
graecizan, B. diffusa and C. schoenanthus as animal feed in
dryland areas. The next step ought to be for some controlled field experiments
with the previous species to assess biomass yield, palatability and in vivo
animal responses, to affirm the generally its positive nutritional
characteristics for cultivation in arid lands.
Acknowledgment
This work was funded by the Deanship
of Scientific Research (DER), King Abdulaziz University, Jeddah, under grant
no. (857-001-D1433). The author, therefore, acknowledge with thanks DSR
technical and financial support.